Remnants of a gamma-ray burst (called GRB 130603B) are visible in these Hubble Space Telescope pictures. Credit: NASA, ESA, and Z. Levay (STScI/AURA)
As astute readers of Universe Today, you likely know what a supernova is: a stellar explosion that signals the end game for certain kinds of stars. Above, however, is a picture of a kilonova, which happens when two really dense objects come together.
This fireball arose after a short-term (1/10 of a second) gamma-ray burst came into view of the Swift space telescope on June 3. Nine days later, the Hubble Space Telescope looked at the same area to see if there were any remnants, and spotted a faint red object that was confirmed in independent observations.
It’s the first time astronomers have been able to see a connection between gamma-ray bursts and kilonovas, although it was predicted before. They’re saying this is the first evidence that short-duration gamma ray bursts arise as two super-dense stellar objects come together.
So what’s the connection? Astronomers suspect it’s this sequence of events:
Two binary neutron stars (really dense stars) start to move closer to each other;
The system sends out gravitational radiation that make ripples in space-time;
These waves make the stars move even closer together;
In the milliseconds before the explosion, the two stars “merge into a death spiral that kicks out highly radioactive material,” as NASA states, with material that gets warmer, gets bigger and sends out light;
The kilonova occurs with the detonation of a white dwarf. While it’s bright, 1,000 times brighter than a nova, it’s only 1/10th to 1/100th the brightness of an average supernova.
An artistic image of the explosion of a star leading to a gamma-ray burst. (Source: FUW/Tentaris/Maciej Fro?ow)
“This observation finally solves the mystery of the origin of short gamma ray bursts,” stated Nial Tanvir of the University of Leicester in the United Kingdom, who is also the lead author.
“Many astronomers, including our group, have already provided a great deal of evidence that long-duration gamma ray bursts (those lasting more than two seconds) are produced by the collapse of extremely massive stars. But we only had weak circumstantial evidence that short bursts were produced by the merger of compact objects. This result now appears to provide definitive proof supporting that scenario.”
Prepare yourself for some goosebumps. The Mercury spacecraft MESSENGER took this series of images of Earth eight years ago today as it swung by the planet (again) en route to its final destination.
Few humans have seen the Earth as an entire orb. Only a handful of missions, all in the Apollo era, have ventured beyond low Earth orbit. The people who traveled furthest were Jim Lovell, Fred Haise and Jack Swigert during Apollo 13, when their spacecraft (which had been crippled by an explosion) looped around the moon on the way home.
MESSENGER is happily traveling around Mercury these days and recently recorded a cool series of images showing the planet as a colorful, spinning sphere. The spacecraft — the first to do an extended stay around that planet — has shown scientists a lot of things, including the discovery of water ice and organics.
It’s Sunday night, and that means it’s time for another Virtual Star Party. This week we had an action-packed episode, with a full house of astronomers. Thanks to relatively clear skies across North America, we had 7 telescopes broadcasting the night sky.
We were also joined by Kevin Nelson, the Vice President of Sales and Marketing for Quantum Scientific Imaging. This is the company that makes high-end CCD cameras that many of our astronomers use. Kevin stuck around for the entire show, showed off a few cameras and answered questions from both inside and outside the Hangout.
We were also joined by a new astronomer, Darryl Van Graal, who was taking wide-field shots of the Ontario skies, hoping for a meteor or an aurora. No luck. 🙁
There were just too many images seen to even provide a partial list. We saw the Ring Nebula, Dumbbell Nebula, Cocoon, Lagoon, Triffid, Eagle, star clusters, galaxies… and so much more.
We gather together every Sunday night on Google+ when it get dark on the West Coast to hold the Virtual Star Party. If you’d like a notification for when it’s happening, make sure you subscribe to the Universe Today channel on YouTube.
Curiosity accomplished Historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182), shown in this context mosaic view of the Yellowknife Bay basin taken on Jan. 26 (Sol 169). The robotic arm is pressing down on the surface at John Klein outcrop of veined hydrated minerals – dramatically back dropped with her ultimate destination; Mount Sharp. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
Curiosity accomplished Historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182), shown in this context mosaic view of the Yellowknife Bay basin taken on Jan. 26 (Sol 169). The robotic arm is pressing down on the surface at John Klein outcrop of veined hydrated minerals – dramatically back dropped with her ultimate destination; Mount Sharp.
Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo Story updated with further details[/caption]
NASA’s mega Mars rover Curiosity is celebrating 1 Year on the Red Planet since the dramatic landing on Aug. 6, 2012 by reveling in a string of groundbreaking science discoveries demonstrating that Mars could once have supported past life – thereby accomplishing her primary science goal – and with a promise that the best is yet to come!
“We now know Mars offered favorable conditions for microbial life billions of years ago,” said the mission’s project scientist, John Grotzinger of the California Institute of Technology in Pasadena.
“Curiosity has landed in an ancient river or lake bed on Mars,” Jim Green, Director of NASA’s Planetary Science Division, told Universe Today.
Curiosity is now speeding onwards towards Mount Sharp, the huge 3.4 mile (5. 5 km) mountain dominating the center of her Gale Crater landing site – and which is the primary destination of the mission.
During Year 1, Curiosity has transmitted over 190 gigabits of data, captured more than 71,000 images, fired over 75,000 laser shots to investigate the composition of rocks and soil and drilled into two rocks for sample analysis by the pair of state-of-the-art miniaturized chemistry labs housed in her belly – SAM & CheMin.
“From the sophisticated instruments on Curiosity the data tells us that this region could have been habitable in Mars’ distant past,” Green told me.
“This is a major step forward in understanding the history and evolution of Mars.”
And just in the nick of time for her 1 year anniversary, the car sized robot just passed the 1 mile (1.6 kilometer) driving mark on Aug. 1, or Sol 351.
Mount Sharp still lies roughly 5 miles (8 kilometers) distant – as the Martian crow flies.
“We will be on a general heading of southwest to Mount Sharp,” Jim Erickson, Curiosity Project Manager of NASA’s Jet Propulsion Laboratory (JPL), told Universe Today in an exclusive interview. See the NASA JPL route maps below.
“We have been going through various options of different planned routes.”
How long will the journey to Mount Sharp take?
“Perhaps about a year,” Erickson told me.
“We have put some new software – called autonav, or autonomous navigation – on the vehicle right after the conjunction period back in March 2013. This will increase our ability to drive.”
The total distance driven by NASA’s Mars rover Curiosity passed the one-mile mark a few days before the first anniversary of the rover’s landing on Mars. This map traces where Curiosity drove between landing at “Bradbury Landing” on Aug. 5, 2012, PDT, (Aug. 6, 2012 (Universal Time and EDT) and the position reached during the mission’s 351st Martian day, or sol, (Aug. 1, 2013). The Sol 351 leg added 279 feet (85.1 meters) and brought the odometry since landing to about 1.05 miles (1,686 meters). Credit: NASA/JPL-Caltech/Univ. of Arizona
“We are trying to make that significantly faster by bringing the new autonav online. That will help. But how much it helps really depends on the terrain.”
So far the terrain has not been problematical.
“Things are going very well and we have a couple of drives under our belt,” said Erickson, since starting the long trek to Mount Sharp about a month ago.
The lower reaches of Mount Sharp are comprised of exposed geological layers of sedimentary materials that formed eons ago when Mars was warmer and wetter, and much more hospitable to microscopic life.
“It has been gratifying to succeed, but that has also whetted our appetites to learn more,” says Grotzinger. “We hope those enticing layers at Mount Sharp will preserve a broad diversity of other environmental conditions that could have affected habitability.”
Indeed, Curiosity’s breakthrough discovery that the surface of Mars possesses the key chemical ingredients required to sustain microbial life in a habitable zone, has emboldened NASA to start mapping out the future of Mars exploration.
“NASA’s Mars program is back on track with the 2016 InSight lander and the 2020 rover,” Jim Green, Director of NASA’s Planetary Science Division, told Universe Today in an interview.
“Successes of our Curiosity — that dramatic touchdown a year ago and the science findings since then — advance us toward further exploration, including sending humans to an asteroid and Mars,” said NASA Administrator Charles Bolden in a statement.
“Wheel tracks now, will lead to boot prints later.”
Following the hair-raising touchdown using with the never before used sky-crane descent thrusters, the science team directed the 1 ton robot to drive to a nearby area of interesting outcrops on the Gale crater floor – at a place called Glenelg and Yellowknife Bay.
Along the way, barely 5 weeks after landing, Curiosity found a spot laden with rounded pebbles at the Hottah outcrop of concretions that formed in an ancient stream bed where hip deep liquid water once flowed rather vigorously.
In February 2013, Curiosity conducted the historic first ever interplanetary drilling into Red Planet rocks at the ‘John Klein’ outcrop inside Yellowknife Bay that was shot through with hydrated mineral veins of gypsum.
The Yellowknife Bay basin looks like a dried up river bed.
This scene combines seven images from the telephoto-lens camera on the right side of the Mast Camera (Mastcam) instrument on NASA’s Mars rover Curiosity on Sol 343 of the rover’s work on Mars (July 24, 2013). The center of the scene is toward the southwest. Credit: NASA/JPL-Caltech/Malin Space Science Systems
Analysis of pulverized portions of the gray colored rocky powder cored from the interior of ‘John Klein’ revealed evidence for phyllosilicates clay minerals that typically form in pH neutral water. These starting findings on the crater floor were unexpected and revealed habitable environmental conditions on Mars – thus fulfilling the primary science goal of the mission.
See herein our context panoramic mosaic from Sol 169 showing the robotic arm touching and investigating the Martian soil and rocks at ‘John Klein’.
And if you take a visit to Washington, DC, you can see our panorama (assembled by Ken Kremer and Marco Di Lorenzo) on permanent display at a newly installed Solar System exhibit at the US National Mall in front of the Smithsonian National Air & Space Museum- details here.
A mosaic by the Mars Science Laboratory Curiosity rover, assembled by Ken Kremer and Marco Di Lorenzo is now part of the permanent Solar System Exhibit outside the National Air and Space Museum on the US National Mall in Washington, D.C. Image courtesy NCESSE.
“We have found a habitable environment [at John Klein] which is so benign and supportive of life that probably if this water was around, and you had been on the planet, you would have been able to drink it,” says Grotzinger, summing up the mission.
Curiosity captured unique and rare view of tiny Martian moons Phobos & Deimos together on Sol 351 (Aug 1, 2013). Look close and see craters on pockmarked Phobos. Credit: NASA/JPL/MSSS, contrast enhanced by Marco Di Lorenzo and Ken KremerOn the long road to Mount Sharp, Curiosity will make occasional stops for science.
This past week she captured rare sky watching images of the diminutive Martian moons – Phobos and Deimos – together!
Meanwhile, Curiosity’s 10 year old sister rover Opportunity Is trundling merrily along and will arrive shortly at her own mountain climbing goal on the opposite of Mars.
And NASA’s next Mars orbiter called MAVEN (for Mars Atmosphere and Volatile Evolution), has just arrived intact at the Kennedy Space Center after a cross country trip aboard a USAF C-17.
Technicians at Kennedy will complete final preparations for MAVEN’s blastoff to the Red Planet on Nov. 18 from the Florida Space Coast atop an Atlas V rocket.
On Tuesday, Aug 6, NASA will broadcast a half day of new programming on NASA TV commemorating the landing and discussing the science accomplished so far and what’s coming next.
And stay tuned for more astonishing discoveries during ‘Year 2’ on the Red Planet from our intrepid rover Curiosity – Starting Right Now !
Curiosity Route Map From ‘Glenelg’ to Mount Sharp
This map shows where NASA’s Mars rover Curiosity landed in August 2012 at “Bradbury Landing”; the area where the rover worked from November 2012 through May 2013 at and near the “John Klein” target rock in the “Glenelg” area; and the mission’s next major destination, the entry point to the base of Mount Sharp. Credit: NASA/JPL-Caltech/Univ. of Arizona
Charlie McDonnell is a phenomenally successful YouTube blogger, with more than 2 million subscribers. And from time to time he likes to wrap his head around complicated topics in space and astronomy.
In this short video, Charlie tackles the implications of what it means to live in an infinite Universe. If the Universe is truly infinite, and there are a finite number of ways that matter can be configured, then if you travel far enough, you will run into duplicates. Continue reading “Are There an Infinite Number of Charlies?”
Scfeenshot from NASA TV of the HTV-4 launch from Japan.
More supplies and a brand new talking robot for International Space Station. The Japan Aerospace Exploration Agency’s (JAXA) HTV-4 Transfer Vehicle launched successfully from the Tanegashima Space Center in Japan, and will rendezvous in six days with the ISS. On board are 3.6 tons of dry cargo, water, experiments and spare parts to the International Space Station. The new robot, a .34 meter (13.4-inch) robot named Kirobo, is designed to be able to have a conversation with its astronaut crewmates and to study how robot-human interactions can help the astronauts in the space environment.
Unlike a Russian Progress vehicle which docks automatically, the HTV-4 will be captured by the Canadarm2 and berthed to the Harmony module. The cargo spacecraft will be commanded to fly within about 40 feet and then hold where Flight Engineer Karen Nyberg will operate the Canadarm2 during the approach and rendezvous of the Kountouri supply vehicle.
A mosaic by the Mars Science Laboratory Curiosity rover, assembled by Ken Kremer and Marco Di Lorenzo is now part of the permanent Solar System Exhibit outside the National Air and Space Museum on the US National Mall in Washington, D.C. Image courtesy Ken Kremer.
Congratulations to Universe Today writer Ken Kremer and his partner in image editing, Marco Di Lorenzo, who have had one of the panoramas they created from the Curiosity rover’s imagery included in a permanent Solar System exhibit outside the National Air and Space Museum on the US National Mall in Washington, D.C. The exhibit is called “Voyage” and was created by the National Center for Earth and Space Science Education (NCESSE) and is sponsored in part by NASA.
Ken said the NCESSE contacted him a few months ago back to use the mosaic — from Sol 169 of Curiosity’s time on Mars — and the project is finally complete. “They liked and chose it because it evokes a human presence on Mars with the rover in the foreground,” Ken said.
The exhibit is a one to 10-billion scale model of our Solar System—spanning 600 meters (6,000 feet) from the National Air and Space Museum to the Smithsonian Castle Building, and Ken and Marco’s image from the Curiosity rover is part of the information about Mars.
Here’s a description of the exhibit from NCESSE website:
“The Voyage exhibition on the National Mall, installed in 2001, was created through a partnership between Challenger Center for Space Science Education, the Smithsonian Institution, and NASA. A summer 2013 update of this exhibition’s content was undertaken by the National Center for Earth and Space Science Education and the Smithsonian Institution, through a grant from the District of Columbia Space Grant Consortium. To learn more, and view photo albums of all Voyage exhibitions, visit the Voyage National Program page.”
Here’s a closeup of Ken and Marco’s mosaic:
Close up of the Mars placard for the Voyager Solar System exhibit. Image courtesy of Ken Kremer.
And a full view of the image is below.
You can learn more about the exhibit at the NCESSE Voyage webpage. Again, congratulations to Ken and Marco!
Curiosity accomplished Historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182), shown in this context mosaic view of the Yellowknife Bay basin taken on Jan. 26 (Sol 169). The robotic arm is pressing down on the surface at John Klein outcrop of veined hydrated minerals – dramatically back dropped with her ultimate destination; Mount Sharp. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
The radiant for the Persieds, looking to the NE from latitide ~30N at around 2AM local. Created by the Author in Starry Night).
Get set for the meteoritic grand finale of summer.
Northern hemisphere summer that is. As we head into August, our gaze turns towards that “Old Faithful” of meteor showers, the Perseids. Though summer is mostly behind us now, “meteor shower season” is about to get underway in earnest.
Pronounced “Pur-SEE-ids,” this shower falls around the second week of August, just before school goes back in for most folks. This time of year also finds many the residents of the northern hemisphere out camping and away from light-polluted suburban skies.
This year also offers a special treat, as the Moon will be safely out of the sky during key observation times. The Moon reaches New phase on August 6th at 5:51 PM EDT/ 9:51 Universal Time (UT) and will be a 32% illuminated waxing crescent around the anticipated peak for the Perseid meteors on August 12th. And speaking of which, the Perseids are infamous for presenting a double-fisted twin peak in activity. This year, the first climax for the shower is predicted for around 13:00 UT on August 12th, favoring Hawaii and the North American west coast, and the second peak is set to arrive 13 hours later at 02:00 UT, favoring Europe & Africa.
Nodal crossing for the Perseid stream and Earth’s orbit sits right around 18:00 to 21:00 UT on August 12th for 2013. The shower derives its name from the constellation Perseus, and has a radiant located near Gamma Persei at right ascension 3 hours 4 minutes and a declination of +58 degrees. Atmospheric velocities for the Perseids are on the high end as meteor showers go, at 59km/sec.
Of course, like with any meteor shower, it’s worth starting to watch a few days prior to the peak date. Although meteor streams like the Perseids have been modeled and mapped over the years, there are still lots of surprises out there. Plus, starting an early vigil is insurance that you at least catch some action in the event that you’re clouded out on game day! Like we mentioned in last week’s post on the Delta Aquarids, the Perseids are already active, spanning a season from July 17th to August 24th.
The Zenithal Hourly Rate for the Perseids is generally between 60-100 meteors. The ZHR is the number of meteors you could expect to see during optimal conditions under dark skies with the radiant directly overhead. Rates were enhanced back in the 1990’s, and 2004 saw a ZHR of 200.
The orbit of comet Swift-Tuttle and its intersection near the Earth’s orbit. (Created by the author using NASA/JPL ephemerides generator).
The source of the Perseids is comet 109P/Swift-Tuttle. Discovered on July 16th-19th, 1862 by astronomers Lewis Swift & Horace Tuttle, Swift-Tuttle is on a 133.3 year orbit and last passed through the inner solar system in late 1992. This comet will once again grace our skies in early 2126 AD.
The Perseids are also sometimes referred to as the “tears of St Lawrence,” after the Catholic saint who was martyred on August 10th, 258 AD. The Perseids have been noted by Chinese astronomers as far back as 36 AD, when it was recorded that “more than 100 meteors flew thither in the morning.” The annual nature of the shower was first described by Belgian astronomer Adolphe Quételet in 1835.
Enhanced rates for the Perseids marked the return of comet Swift-Tuttle in the 1990s. Recent years have seen rates as reported by the International Meteor Organization at a ZHR=175(2009), 91(2010), 58(2011), & a resurgence of a ZHR=122 last year.
Just what will 2013 bring? There’s one truism in meteor observing—you definitely won’t see anything if you do not get out and observe. Meteor shower observing requires no equipment, just clear skies and patience. Watch in the early hours before dawn, when the rates are highest. Meteors can occasionally be seen before midnight, but are marked by lower rates and slow, stately trains across the sky. Some suggest that best viewing is at a 45 degree angle away from the radiant, but we maintain that meteors can appear anywhere in the sky. Pair up with a friend or two and watch in opposite directions to increase your meteor-spotting chances.
We also like to keep a set of binoculars handy to examine those smoke trains left by bright fireballs that may persist seconds after streaking across the sky.
And speaking of which, there has also been some spirited discussion over the past week as to whether or not the Perseids produce more fireballs than any other shower. I certainly remember seeing several memorable fireballs from this shower over the years, although the Geminids, Leonids and Taurids can be just spectacular on active years. The stated r value of the Perseids is one of the lowest at 2.2, suggesting a statistically high percentage of fireballs.
And in the realm of the strange and the curious, here are just a few phenomena to watch/listen for on your Perseid vigil;
– Can you “hear” meteors? Science says that sounds shouldn’t carry through the tenuous atmosphere above 50 kilometres up, and yet reports of audible meteors as a hiss or crackle persist. Is this an eye-brain illusion? Researchers in 1988 actually studied this phenomenon, which is also sometimes reported during displays of aurora. If there’s anything to it, the culprit may be the localized generation of localized electrophonic noises generated by Extra/Very Low Frequency electromagnetic radiation.
– Can meteor streaks appear colored? Green is often the top reported hue.
– Can meteors appear to “corkscrew” during their trajectory, or is this an illusion?
A Perseid very near the shower radiant during the 2012 shower. (Photo by author).
Wide-field photography is definitely a viable option during meteor showers. Just remember to bring extra charged batteries, as long exposure times will drain modern DSLRs in a hurry!
And did you know: you can even “listen” to meteor pings on an FM radio or portable TV? This is a great “rain check” option!
And there’s still real science to be done in the world of meteor shower studies. The International Meteor Organization welcomes counts from volunteers… and be sure to Tweet those Perseid sightings to #Meteorwatch.
Also be sure to check out the UK Meteor Observation Network, which has just launched their live site with streaming images of meteors as they are recorded.
Good luck, clear skies, and let the late 2013 meteor shower season begin!
-And be sure to post those Perseid pics to the Flickr forum on Universe Today… we’ll be doing photo essay roundups from observers around the world!
It’s time for another Weekly Space Hangout, where we give you a rundown of the big space news stories of the week, from a team of scientists and space journalists.
We record the Weekly Space Hangout live on Google+ every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch the show live here on Universe Today, or the archived version on YouTube.
Looking east from latitude 30 north on August 3rd, 30 minutes before sunrise. (Created by the author in Stellarium).
Can you feel the heat?
It’s not just your imagination. The northern hemisphere is currently in the midst of the Dog Days of Summer. For many, early August means hot, humid days and stagnant, sultry nights.
The actual dates for the Dog Days of Summer vary depending on the source, but are usually quoted as running from mid-July to mid-August. The Old Farmer’s Almanac lists the Dog Days as running from July 3rd through August 11th.
But there is an ancient astronomical observation that ties in with the Dog Days of Summer, one that you can replicate on these early August mornings.
The sky was important to the ancients. It told them when seasons were approaching, when to plant crops, and when to harvest. Ancient cultures were keen observers of the cycles in the sky. Cultures that were “astronomically literate” had a distinct edge over those who seldom bothered to note the goings on overhead.
The flooded Temple of Isis on the island of Philae circa 1905. (Credit: Wikimedia Commons under an Attribution-Share Alike 2.5 license. Author H.W. Dunning).
Sirius was a key star for Egyptian astronomers. Identified with the goddess Isis, the Egyptian name for Sirius was Sopdet, the deification of Sothis. There is a line penned by the Greco-Roman scholar Plutarch which states:
“The soul of Isis is called ‘Dog’ by the Greeks.”
Political commentary? A mis-translation by Greek scholars? Whatever the case, the mythological transition from “Isis to Sothis to Dog Star” seems to have been lost in time.
These astronomer-priests noted that Sirius rose with the Sun just prior to the annual flooding of the Nile. The appearance of a celestial object at sunrise is known as a heliacal rising. If you can recover Sirius from behind the glare of the Sun, you know that the “Tears of Isis” are on their way, in the form of life-giving flood waters.
Sopdet as the personification of Sirius (note the star on the forehead) Wikimedia Commons image under an Attribution Share Alike 3.0 license. Author Jeff Dahl).
In fact, the ancient Egyptians based their calendar on the appearance of Sirius and what is known as the Sothic cycle, which is a span of 1,461 sidereal years (365.25 x 4) in which the heliacal rising once again “syncs up” with the solar calendar.
It’s interesting to note that in 3000 BC, the heliacal rising of Sirius and the flooding of the Nile occurred around June 25th, near the summer solstice. This also marked the Egyptian New Year. Today it occurs within a few weeks of August 15th, owing to precession. (More on that in a bit!)
By the time of the Greeks, we start to see Sirius firmly referred to as the Dog Star. In Homer’s Iliad, King Priam refers to an advancing Achilles as:
“Blazing as the star that cometh forth at Harvest-time, shining forth amid the host of stars in the darkness of the night, the star whose name men call Orion’s Dog”
The Romans further promoted the canine branding for Sirius. You also see references to the “Dog Star” popping up in Virgil’s Aenid.
Over the years, scholars have also attempted to link the dog-headed god Anubis to Sirius. This transition is debated by scholars, and in his Star Names: Their Lore and Meaning, Richard Hinckley Allen casts doubt on the assertion.
Sirius as the shining “nose” of the constellation Canis Major. (Created by the author using Starry Night).
Ancient cultures also saw the appearance of Sirius as signifying the onset of epidemics. Their fears were well founded, as summer flooding would also hatch a fresh wave of malaria and dengue fever-carrying mosquitoes.
Making a seasonal sighting of Sirius is fun and easy to do. The star is currently low to the southeast in the dawn, and rises successively higher each morning as August rolls on.
The following table can be used to aid your quest in Sirius-spotting.
Latitude north
Theoretical date when Sirius can 1st be spotted
32°
August 3rd
33°
August 4th
34°
August 5th
35°
August 6th
36°
August 7th
37°
August 8th
38°
August 9th
39°
August 10th
40°
August 11th
41°
August 12th
42°
August 13th
43°
August 14th
44°
August 15th
45°
August 16th
46°
August 17th
47°
August 18th
48°
August 19th
49°
August 20th
50°
August 21st
Thanks to “human astronomical computer extraordinaire” Ed Kotapish for the compilation!
Note that the table above is perpetual for years in the first half of the 21st century. Our friend, the Precession of the Equinoxes pivots the equinoctial points to the tune of about one degree every 72 years. The Earth’s axis completes one full “wobble” approximately every 26,000 years. Our rotational pole only happens to be currently pointing at Polaris in our lifetimes. Its closest approach is around 2100 AD, after which the north celestial pole and Polaris will begin to drift apart. Mark your calendars—Vega will be the pole star in 13,727 AD. And to the ancient Egyptians, Thuban in the constellation Draco was the Pole Star!
The Colossi of Memnon Near Luxor, just one of the amazing architectural projects carried out by the ancient Egyptians. (Photo by author).
Keep in mind, atmospheric extinction is your enemy in this quest, as it will knock normally brilliant magnitude -1.46 Sirius a whopping 40 times in brightness to around magnitude +2.4.
Note that we have a nice line-up of planets in the dawn sky (see intro chart), which are joined by a waning crescent Moon this weekend. Jupiter and Mars ride high about an hour before sunrise, and if you can pick out Mercury at magnitude -0.5 directly below them, you should have a shot at spotting Sirius far to the south.
And don’t be afraid to “cheat” a little bit and use binoculars in your quest… we’ve even managed on occasion to track Sirius into the broad daylight. Just be sure to physically block the Sun behind a building or hill before attempting this feat!
Of course, the heliacal rising of Sirius prior to the flooding of the Nile was a convenient coincidence that the Egyptians used to their advantage. The ancients had little idea as to what they were seeing. At 8.6 light-years distant, Sirius is the brightest star in Earth’s sky during the current epoch. It’s also the second closest star visible to the naked eye from Earth. Only Alpha Centauri, located deep in the southern hemisphere sky is closer. The light you’re seeing from Sirius today left in early 2005, back before most of us had Facebook accounts.
Sirius also has a companion star, Sirius B. This star is the closest example of a white dwarf. Orbiting its primary once every 50 years, Sirius B has also been the center of a strange controversy we’ve explored in past writings concerning Dogon people of Mali.
Sirius B is difficult to nab in a telescope, owing to dazzling nearby Sirius A. This feat will get easier as Sirius B approaches apastron with a max separation of 11.5 arc seconds in 2025.
Some paleoastronomers have also puzzled over ancient records referring to Sirius as “red” in color. While some have stated that this might overturn current astrophysical models, a far more likely explanation is its position low to the horizon for northern hemisphere observers. Many bright stars can take on a twinkling ruddy hue when seen low in the sky due to atmospheric distortion.
Let the Dog Days of Summer (& astronomy) begin! (Photo by author).
All great facts to ponder during these Dog Days of early August, perhaps as the sky brightens during the dawn and your vigil for the Perseid meteors draws to an end!
